| In recent years,with the rapid economic development,changes in dietary structure,and excessive intake of high-sugar and high-fat foods,the incidence of chronic diseases such as cardiovascular disease,diabetes,and obesity among Chinese residents remains high.Buckwheat,as an important cereal crop in my country,contains cellulose,polyphenols,carotenoids and other biologically active substances,and has various functional activities such as hypoglycemic and lipid-lowering,anti-inflammatory,antioxidant,etc.,which are useful for improving dietary structure and preventing chronic diseases.It plays an important role in increasing the consumption of buckwheat.In order to improve the comprehensive utilization level of buckwheat resources and give full play to its health benefits.In this paper,cellulose was extracted from buckwheat bran by alkaline hydrolysis and enzymatic hydrolysis,and buckwheat bran cellulose nanocrystals(CNC)were prepared using three methods(sulfuric acid hydrolysis,acetic acid hydrolysis and sodium periodate oxidation)as raw materials,and their characterization and physicochemical properties were explored;a safe,non-toxic and high-yield acetic acid hydrolyzed CNC was selected and modified by esterification to improve its adsorption capacity for oil;the lipid-lowering activity and safety of CNC and esterification-modified CNC were evaluated by in vitro simulation experiments such as fat in vitro simulated digestion and fat absorption in vitro,and in vivo experiments such as rapid digestion in rats and feeding of high-fat mice;and a CNC gel particle based on sodium alginate and a cellulose nanoparticle based on whey protein isolate were developed using CNC as raw material.It provides theoretical basis and data support for the high-value utilization of buckwheat industrial by-products in the food field.The main findings of this study are as follows:(1)The buckwheat bran was crushed and sieved,soaked in water,anhydrous ethanol and3% Na OH solution in order to remove impurities,and then buckwheat cellulose was obtained through enzymatic hydrolysis,alkali hydrolysis and bleaching.Three kinds of buckwheat bran CNCs were prepared by hydrolysis of 64% sulfuric acid at 45 °C for 60 min,88% acetic acid at 95 °C for 60 min and 0.33% sodium periodate oxidation for 4 d using this as raw material.It was found that the higher the cellulose content of CNC,the lower the yield and the smaller the size with the enhancement of hydrolysis and oxidation capacity.The yields of sulfuric acid,acetic acid hydrolysis and sodium periodate oxidation were34.2%,62.3% and 72.5%,respectively.(2)The structure of CNC was characterized by infrared spectroscopy,X-ray diffraction and other instruments,and then the physical and chemical properties of CNC were explored and studied.It was found that the CNCs obtained by the three methods all had obvious rod-like structure,similar Fourier transform infrared peaks,thermal stability and crystal structure.The adsorption performance of buckwheat cellulose was significantly improved after nano-processing.Taking acetic acid hydrolyzed CNC as an example,the adsorption capacities of cellulose for water,oil,glucose and heavy metal lead ions were 5.29 g/g,4.96g/g,3.67 mg/g and 165.10 mg/g,respectively,and the adsorption capacities after nanometerization were increased to 18.70 g/g,35.80 g/g,16.97 mg/g and 422 mg/g,respectively.(3)Using the direct esterification(DE)method,the N,N’-carbonyldiimidazole(CDI)catalysis method and the acid chloride esterification(ACE)method to convert palmitic acid to the ester group.The form was grafted on top of CNC,and it was characterized,and its adsorption performance was verified at the same time.It was found that,among the three methods,CDI catalysis method can not only successfully obtain esterification modified CNC,but also take into account the characteristics of environmental protection and pollution-free.Compared with CNC,its adsorption capacity for water and glucose decreased,but the adsorption capacity for oil was improved,and the maximum adsorption capacity increased from 35.80 g/g to 46.91 g/g.At the same time,the esterification substitution degree of esterification modified CNC was measured,and the result was 0.03.(4)The lipid-lowering activity and safety of CNC and esterification-modified CNC were verified by in vitro simulation experiments such as p H-start and intestinal valgus,and in vivo experiments such as SD rat rapid digestion experiments and long-term feeding animal experiments.It was found that compared with cellulose,CNC and esterification-modified CNC can effectively reduce the hydrolysis of fat and prevent fat from passing through intestinal cells into the human body.Among them,CNC reduced the hydrolysis of triglycerides by 49.11% and fat transport by 43.88%.In the long-term feeding experiment,CNC can effectively reduce the fat absorption of mice by 57.95%.At the same time,from the perspective of mouse organs,blood and intestinal indicators,CNC does not bring safety hazards to mice.(5)A sodium alginate-based CNC gel particle and a whey protein isolate-based cellulose nanoparticle were developed.The addition of CNC to the sodium alginate gel particles improved the water retention,gel strength and storage stability of the gel particles.The glucose adsorption capacity and antioxidant capacity of both CNC gel particles and nanoparticle products were significantly improved.At the same time,compared with CNC,gel particles and nanoparticles reduced intestinal fat transport by 19.8% and 22.6%,and fat absorption in mice by 39.6% and 39.2%,respectively.It was proved that both products well preserved the lipid-lowering activity of CNC.To sum up,in this paper,cellulose was obtained from buckwheat bran and nano-processed,and palmitic acid was grafted on CNC by esterification modification.Subsequently,a series of in vitro and in vivo experiments were designed to verify the lipid-lowering functional activity of CNC and palmitate-modified CNC through fat adsorption.Finally,in order to better use CNC in the food industry,a sodium alginate-based CNC gel particle and a whey protein isolate-based cellulose nanoparticle were developed,and their physicochemical properties were characterized,and the lipid-lowering activity of the two products was verified. |
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